Each unit cell of a solid oxide fuel cell (SOFC) includes an electrolyte having oxygen ion conductivity and an anode and a cathode disposed on both surfaces thereof. When oxygen and hydrogen are supplied to respective electrodes, the oxygen ion produced by a reduction reaction of oxygen at the cathode is transported to the cathode through the electrolyte and then reacts with hydrogen supplied to the anode, thus forming water. As such, in the course of the electrons produced at the anode being transported to the cathode and consumed, the electrons flow to external circuits, thereby producing electric energy.
The unit cells are connected by means of a connector. More specifically, the connector typically functions to electrically connect the anode of one cell and the cathode of a neighboring cell to each other. Also, the connector should play a role in physically preventing mixing between air gas supplied to the anode and fuel gas supplied to the cathode. As the connector, a metal connector and a ceramic connector are mainly used.
The ceramic connector has good mechanical properties at high temperature, but is not dense, so gas may leak, a reaction with an electrode may occur, or stripping from an electrode may take place during operation of the fuel cell.